1. Field of the Invention
The present invention relates to a super abrasive tool and a process for producing the same. More particularly, the present invention relates to a super abrasive tool which maintains sufficient protrusion of super abrasive grains, causes no releasing of the super abrasive grains nor loading and has excellent cutting ability and a process for producing the same.
2. Description of Related Art
It is preferable that no releasing of abrasive grains takes place in a super abrasive tool. In particular, absolutely no releasing of super abrasive grains is allowed for CMP conditioners used for conditioning of CMP pads. In Japanese Patent Application Laid-Open No. Heisei 10(1998)-15819, a CMP conditioner in which super abrasive grains protrude from the working surface by heights in the range of 5 to 30% of the average diameter of grains is proposed as the CMP conditioner which can perform dressing of polishing pads for CMP in a short time, has no possibility of releasing of super abrasive grains and provide the polishing pad with excellent flatness. However, since a slurry formed by polishing is not removed sufficiently although releasing of the super abrasive grains can be prevented when the super abrasive grains are embedded deeply, improvement in the removal of the slurry formed by polishing is attempted by forming depressed portions such as slits and dimples or portions having no super abrasive grains on the working surface. In Japanese Patent Application Laid-Open No. Heisei 12(2000)-153463, a process for producing a CMP conditioner which comprises coating a working surface of a base metal with an adhesive at a plurality of spots separated by a specific distance between each other, temporarily attaching super abrasive grains on the adhesive on the spots and fixing the temporarily attached super abrasive grains by plating is proposed as the process for producing a CMP conditioner which exhibits suppressed abrasion of a polishing pad, maintains the surface in a constant condition and causes little releasing of the super abrasive grains. The removal of the slurry formed by polishing is improved by disposing super abrasive grains in the scattered spots and the sharpness of the CMP conditioner can be improved by decreasing the working number of the super abrasive. However, it is necessary that the depth of the embedded super abrasive grains be increased to prevent releasing of the super abrasive grains.
The present invention has an object of providing a super abrasive tool which maintains sufficient protrusion of super abrasive grains, causes no releasing of the super abrasive grains nor loading and has excellent cutting ability and a process for producing the same.
As the result of intensive studies by the present inventor to achieve the above object, it was found that a super abrasive tool which causes no releasing of the grains, can maintain sufficient protrusion of super abrasive grains and has excellent cutting ability can be obtained by forming protrusions in a bond layer on the working surface of the super abrasive tool, disposing one super abrasive grain at the top of each protrusion and adjusting the average height from the flat surface of the bond layer to the top of the super abrasive grain is in the range of 0.3 to 1.5 times the average diameter of the super abrasive grains. The present invention has been completed based on the knowledge.
The present invention provides:
(1) A super abrasive tool comprising super abrasive grains which are arranged on a working surface in a scattered manner and fixed with a bond layer, wherein the bond layer has protrusions and a flat surface at portions other than the protrusions, one super abrasive grain is disposed at each protrusion and an average height from the flat surface of the bond layer to a top of the super abrasive grain is in a range of 0.3 to 1.5 times an average diameter of the super abrasive grains;
(2) A super abrasive tool described in (1), wherein the protrusion has an average diameter at the flat surface of the bond layer in a range of 1.02 to 4 times the average diameter of the super abrasive grains;
(3) A super abrasive tool described in (1), wherein a height from the flat surface of the bond layer to a top of each super abrasive grain is distributed in a range of 0 to 1.8 times the average diameter of the super abrasive grain;
(4) A super abrasive tool described in (3), wherein super abrasive grains are further disposed on the flat surface of the bond layer;
(5) A super abrasive tool described in (1), which is a CMP conditioner;
(6) A process for producing a super abrasive tool which comprises forming, in a spacer having a thickness in a range of 0.3 to 1.5 times an average diameter of super abrasive grains, holes each having a cylindrical portion which is formed at a lower face of the spacer and has a diameter smaller than the average diameter of super abrasive grains and a portion which is connected to the cylindrical portion and has a diameter continuously increasing from the diameter of the cylindrical portion to a diameter in a range of 1.02 to 4 times the average diameter of super abrasive grains at an upper face of the spacer; placing one super abrasive grain in each hole formed above; fixing the super abrasive grains by forming a bond layer on the upper face of the spacer; and removing the spacer;
(7) A process described in (6), wherein a diameter or a length of the cylindrical portion of the hole formed at the lower face of the spacer is different among the holes;
(8) A process described in (6), wherein cylindrical holes having a same length as the thickness of the spacer are further formed in the spacer and one super abrasive grain is disposed in each of said cylindrical holes; and
(9) A process described in (6), wherein the bond layer is formed on the spacer, which has super abrasive grains placed in a manner such that one super abrasive grain is placed in each hole, by conducting plating after a pressure of a plating fluid at the upper face of the spacer is made higher than a pressure of the plating fluid at the lower face of the spacer in a plating bath.